X0306 4 2021-02-22 0 0001680581 Fulcrum Therapeutics, Inc. FULC 0001779120 Thomson Peter G. C/O FULCRUM THERAPEUTICS, INC. 26 LANDSDOWNE STREET CAMBRIDGE MA 02139 0 1 0 0 VP Finance & Accounting Common Stock 2021-02-22 4 M 0 5000 7.84 A 20212 D Common Stock 2021-02-22 4 S 0 5000 14.7163 D 15212 D Stock Option (right to buy) 7.84 2021-02-22 4 M 0 5000 0.00 D 2029-01-21 Common Stock 5000 50471 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 16, 2020. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.31 to $15.03, inclusive. The reporting person undertakes to provide to Fulcrum Therapeutics, Inc., any security holder of Fulcrum Therapeutics, Inc. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote (2) to this Form 4. The shares underlying the option are scheduled to vest in equal quarterly installments over four years beginning on the vesting commencement date of January 1, 2019, subject to continued service. Exhibit Index: 24.1 Power of Attorney /s/ Peter Thomson 2021-02-24